1. Technical Field
This disclosure relates to hydro-mechanical forming tool having a chamber that is filled with a liquid during a method of reducing the cycle time for a hydro-mechanical forming operation.
2. Background Art
In one type of hydro-mechanical drawing process, a sheet metal blank is formed by drawing the blank onto a punch with the area below the blank being filled with a liquid. The liquid is compressed and forms the blank against the punch. The liquid eliminates the need for one side of the tooling.
The required pressure to completely form a production part is dictated by the tightest local radius of the part to be formed. A large press is required to apply maximum pressure to the entire surface of the blank that is required to form relatively small tight local radii.
Hybrid hydro-mechanical drawing followed by conventional forming in two-sided dies is a known process being conducted in a single tool, in which the blank is initially formed by hydro-mechanical drawing. Then, local features that may have tight local radii are formed subsequently in a two-sided die. Hybrid hydro-mechanical drawing enables deeper drawing of the blank compared to forming on a conventional press. However, the maximum elongation of the blank usually remains within the forming limit diagram of the material being formed.
One problem with hydro-mechanical drawing is that a relatively long cycle time is required, which can approach one minute for forming large automotive panels. The long cycle time is required because a substantial volume of water (several hundreds of liters) must be delivered to the tool and drained from the tool within each forming cycle.
Substantial energy and time is required to generate sufficient pressure for forming operations. Specialized equipment, including a several thousand ton hydraulic tool, may be required to implement the hydro-mechanical drawing process. The size of the press can be significantly reduced, and pre-existing press equipment in manufacturing plants can be used if the volume of liquid required to form a part is substantially reduced. There is a need for a process and tooling that focuses the hydro-mechanical force in limited areas where the application of pressure applied by the liquid is most beneficial.
The above problems are addressed by applicant's developments as summarized below.